Injection of substances into avian eggs is employed for many reasons, including to decrease post-hatch mortality rates, increase the potential growth rates or eventual size of the resulting chicken, and even to influence the gender determination of the embryo. Similarly, viruses have been injected into live eggs to produce viruses for use in vaccines.
Examples of substances which have been introduced into embryonated poultry eggs via in ovo injection include live culture vaccines, antibiotics, vitamins, and competitive exclusion media (e.g., a live replicating organism). Specific examples of treatment substances are described in U.S. Pat. No. 4,458,630 to Sharma et al, and U.S. Pat. No. 5,028,421 to Fredericksen et al. See also U.S. Pat. No. 4,458,630 to Sharma et al., U.S. Pat. No. 4,681,063 to Hebrank, and U.S. Pat. No. 5,158,038 to Sheeks et al.
In using in ovo injection, the location of the injection will vary depending on the desired result and the injectable being used. U.S. Pat. No. 4,458,630 to Sharma describes injection into the region defined by either the amnion or the yolk sac. Published PCT application W093/15185 describes injection of substances into the air cell of embryonated eggs; PCT application W093/14629 describes injection into the muscle tissue of the embryo contained within the egg.
U.S. Pat. No. 5,136,979 to Paul describes a modular injection system for avian embryos. The system comprises a generally horizontally oriented tooling plate with an opening therethrough, an injector resting generally vertically in the opening in the tooling plate with a lower portion of the injector depending downwardly below the tooling plate and an upper portion of the injector resting at or above the tooling plate. Means are included for raising and lowering the tooling plate and the injector therewith so that when the plate is lowered and the lower portion of the resting injector strikes an egg to be injected, the resting injector stops while the tooling plate proceeds downwardly until the injector disengages from the tooling plate and is free to move in a translational direction independent of the tooling plate. When the tooling plate is raised it reengages the injector and carries it upwardly and away from the egg.
This apparatus described in Paul et al. has been used in the high-speed commercial injection of live bird eggs, and has gained wide acceptance in the industry. The success of this apparatus has made possible the in ovo injection of increasingly sophisticated, and expensive, materials, such as vaccines. The size and location of the internal compartments and structures of avian eggs are, however, inherently variable, and some eggs are occasionally injected in non-optimal sites. Increased injection accuracy is desirable to minimize mis-directed injections, in order to avoid wasting injectables and avoid ineffective injection. Achieving increased injection accuracy requires obtaining useful, real-time information from the interior of the egg during the injection process, which has not heretofore been achieved by prior automated in ovo injection methods and apparatus.